Phosphorus-copper base brazing alloy

ABSTRACT

A solid phos-copper base or silver-phos-copper base brazing alloy component for forming a brazed joint with a raised shoulder, little to no black oxide, and improved corrosion resistance. The brazing alloys of the present invention are visually distinguishable from copper and copper alloy parts. The solid brazing components of the present invention may be used in forming brazed joints at low brazing temperatures and result in a joint that is strong, ductile, smooth and corrosion resistant. The solid brazing components are provided in the form of wire, strip, foil or preform, and thus are advantageously used in a wide variety of brazing applications including copper tubing. The brazing components of the present invention are made of an alloy having a liquidus temperature above 840° F. and consist essentially of about 4-9% phosphorus, about 0.1-10% tin, up to about 4% antimony, about 0.1-15% nickel, up to about 3% silicon, up to about 18% silver, up to about 3% manganese, with the balance being copper. Exemplary embodiments include about 6-15% silver and/or 5-8% nickel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional application of and claims the benefitof priority to U.S. application Ser. No. 10/628,651 filed Jul. 28, 2003which claims the benefit of and priority to U.S. Provisional ApplicationSer. No. 60/452,255, filed Mar. 5, 2003, and is also acontinuation-in-part of commonly owned, U.S. patent application Ser. No.10/226,672, filed Aug. 23, 2002, which is now abandoned. Each of theabove-identified applications is incorporated by reference herein intheir entirety.

FIELD OF THE INVENTION

This invention relates to a solid copper brazing component and methodfor forming a brazed joint, and in particular, a brazing component forjoining copper and copper alloys.

BACKGROUND OF THE INVENTION

Copper and copper alloys have been brazed successfully for many yearswith metals comprising the phosphorus-copper alloys, also known asphos-copper alloys. Silver is often added to the base metals toaccomplish special features for a wide variety of applications. Thesealloys are generally known as silver-phos-copper alloys. Silver brazingalloys, composed primarily of silver, copper, zinc, tin, nickel,manganese, and cadmium, are used to braze ferrous and non-ferrous metalsand alloys. These silver brazing alloys are designed to work at lowtemperatures and to provide strong, ductile joints.

Additions of other elements, such as tin, antimony, nickel or silver, tophos-copper and silver-phos-copper alloys have been made in an effort tolower the melting range temperatures or to reduce the phosphorus contentto increase ductility. For example, U.S. Pat. No. 5,066,456 disclosesthat the addition of tin and antimony up to six percent each to aphos-copper based alloy lowers brazing temperatures.

Air conditioning coils, heat exchangers, water coolers and other coppercoils are manufactured by connecting copper tubing and fittings bybrazing with phos-copper or silver-phos-copper brazing alloys. Thesealloys produce strong, ductile brazes, but the industry has longexperienced a relatively high percentage of leaks after brazing,particularly with BCuP-2 alloys. Most leaks are caught on the productionfloor during testing and are repaired. This double work of brazing andtesting is very costly. More damaging, very tiny leaks can evade factorytesting and end up as warranty work in the field, which is bothexpensive and damaging to the company's brand image.

The phos-copper alloys now on the market all range within a solidustemperature of 1310° F. to a liquidus temperature of 1500° F. Alloys ofeven higher phosphorus content, up to 8%, are now in use to enhanceproductivity because of their lower operating temperature costconsiderations. The non-silver alloys in this group are the mostcommonly used in industry and contain 7% to 7.4% phosphorus, the balancebeing copper. The fact that these phos-copper alloys flow and join verywell is problematic in that they also flow very thinly. Torch andfurnace brazing is performed as rapidly as possible to achieve goodproductivity. While these alloys are quick to braze, they are difficultto observe for soundness. The entire 360° of the brazed joint must becarefully viewed by the operator, for it is here that a correction, ifneeded, should be made. These thin-flowing alloys produce only a verysmall cap, or shoulder, around the pipe at the fitting junction. Thealloys are thin-flowing in that they flow like a heavy coating of paint,instead of more thickly as in a putty used to seal a ⅛″ crack.

Even a skilled brazer cannot tell 100% of the time that he has a totallyleak-free connection by visually looking at his completed braze. In someplaces on a given braze connection, the brazing alloy can be seen to bein place as a shoulder between the two parts, while in other places thealloy drops in the adjoining area (the capillary) without forming anynoticeable shoulder. When viewing this very closely, the operator canoften see that the joint appears to be 100% sound, but he can't becertain of it. Most air conditioning companies submerge each coppercoil, which comprises perhaps 100 brazes, into a water tank, and airpressure is added to this coil to determine if there are any leaks.Wherever leaks are found, brazing must be repeated.

The now-in-use phos-copper alloys, as described above, could be modifiedto form an advantageous cap by lowering the phosphorus contentsignificantly. However, doing so is not feasible because the liquidustemperature rises to a point of endangering the copper being brazed. Itis noteworthy that silver in the range of 6-15%, when added to thephos-copper alloys described above, lowers the solidus temperature to1190° F., allows the phosphorus contents to be reduced as much as 2%,allows the alloy to flow in a much thicker manner, and effects anoticeable cap or shoulder to the brazed area. The popular 15%silver-phos-copper alloy has the consistency of hot taffy when hotenough to braze, and easily forms a large cap or shoulder at the jointarea. This visible fillet is quickly seen by the operator and anyomission in the braze can be remedied. However, the addition of silveris quite expensive.

Another serious deterrent to being able to observe the quality of coppertubing brazed with phos-copper or silver-phos-copper brazing alloys isthe formation of a black oxide that is formed on the actual brazesurface and on the adjacent copper pipe. Because the braze and thecopper pipe all turn black, it is difficult to closely inspect theactual braze.

In addition to the initial soundness of the brazed joint, the corrosionresistance of the joint is of great importance. Brazed parts are used incorrosive environments of varying degree, for example, the marineenvironment, sewer treatment facilities and underground. The BCuP-5alloy (80Cu-5P-15Ag) is typically used whenever corrosion is asignificant factor. However, further improvement in corrosion resistanceis desirable.

There is thus a need for a phos-copper base alloy system that brazes atlow temperatures, forms a noticeable cap or shoulder to facilitatevisual inspection, does not form black oxide to any extent that willobscure visual inspection, and provides high corrosion resistance.

SUMMARY OF THE INVENTION

The present invention provides a solid phos-copper base brazing alloycomponent suitable for forming a brazed joint with a raised shoulder andlittle to no black oxide, that is visually distinguishable from copperor copper alloy parts, and provides high corrosion resistance. Thebrazing filler metal of the present invention incorporates anadvantageously low brazing temperature range and is both ductile, smoothand corrosion resistant. The brazing alloys of the present invention canbe extruded into wire and optionally formed into various preforms orfabricated into strips or foil, thereby providing a solid brazingcomponent suitable for numerous brazing applications, such as brazinglarge copper pipe fittings. To this end, a brazing alloy is cast andthen fabricated into wire, strip, foil or preform. For example, a castbillet may be extruded into wire, which may be further formed into apreform. The component is made of an alloy having a liquidus temperatureabove 840° F. (449° C.) and which consists essentially of about 4% toabout 9% phosphorus; about 0.1% to about 10% tin; about 0.1 to about 15%nickel; up to about 3% silicon; up to about 18% silver; up to about 4%antimony; up to about 3% manganese, and the balance copper. In exemplaryembodiments, the alloy includes about 1% to about 18% silver and/orabout 3% to about 10% nickel, and advantageously 5-8% nickel.

The present invention further provides a method for forming a brazingcomponent of the composition described above, wherein a molten alloy iscontinuously cast into a billet, which is then fabricated into a wire orthick strip. The wire may then be drawn to a desired diameter, and thestrip may be rolled to a desired thickness or to a thin foil. The wiremay also be further formed into a preform. To form a brazed joint, thesolid brazing component is placed between two metal parts, such ascopper tubing, the component is heated to a temperature to melt at leasta major portion of the brazing alloy, thereby causing it to wet and flowbetween the parts, and then the alloy is cooled. The brazing componentof the present invention produces a substantial raised shoulder or capabout the brazed joint, which is a visible sign to the operator that thejoint is sound.

The brazing component of the present invention further produces a brazedjoint with little to no black oxide that can obscure the operator's viewof the soundness of the joint. In addition, the combination of alloyingelements significantly reduces the melting range of these brazing fillermetals, thereby providing a cost savings by reducing the use ofexpensive fuel gases and the time required of the brazing process. Theaddition of nickel in combination with tin may further provide anincrease in hardness and an improvement in corrosion resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description given below, serve to explain the invention.

FIG. 1 is a graph depicting the improvement in corrosion resistance forsilver-phos-copper alloys of the present invention containing 5-8%nickel in combination with tin, as compared to BCuP alloys of the priorart.

FIG. 2 is a graph depicting the improvement in corrosion resistance forphos-copper alloys of the present invention containing 3-8% nickel incombination with tin, as compared to BCuP alloys of the prior art.

DETAILED DESCRIPTION

The present invention provides phos-copper base brazing alloys that arematerially improved in their properties by the addition of specifiedamounts of tin and nickel, and further by specified additions of siliconand/or silver. The melting range can be lowered, narrowed or broadened.In other words, the specified alloy additions lower one or more of theliquidus, major thermal arrest (MTA) or solidus temperatures. As usedherein, the liquidus temperature refers to that temperature at which thealloy is completely liquid, i.e. at which the alloy finishes meltingupon heating. The solidus temperature refers to that temperature atwhich a metal is completely solid, i.e., at which the alloy begins tomelt upon heating. Thus, the brazing temperature range extends from thesolidus temperature to the liquidus temperature. The brazingtemperature, or melting temperature at which the alloy wets and flows,is generally considered to be between the solidus and liquidustemperatures. Some alloys exhibit thermal arrests between the solidusand liquidus, which may be observed on the cooling curve for a givenalloy, with the major thermal arrest (MTA) temperature indicating themelting temperature of a major portion of the alloy. For alloys that doexhibit a MTA, the brazing temperature is generally considered to be ator near the MTA. For alloys that do not exhibit a MTA, the brazingtemperature (i.e., temperature at which a major portion of the alloy ismelted) is generally considered to be at or near the liquidustemperature.

The alloys of the present invention form a large cap, or shoulder,during the brazing process that is clearly visible, and they do so at abrazing temperature that has not been possible with phos-copper brazingalloys in the past without the addition of silver to the composition ofthe alloys. In fact, the phos-copper base alloys of the presentinvention which include tin and nickel, and advantageously silicon, willform a cap or shoulder similar to or superior to silver-phos-copperalloys of the prior art, and will do so at lower brazing temperaturesthan the prior art silver-containing alloys, and will exhibit greatercorrosion resistance. The phos-copper base alloys of the presentinvention which include silver, tin and nickel, and advantageouslysilicon, also form a cap or shoulder similar to or superior tosilver-phos-copper alloys of the prior art and will do so atsignificantly lower brazing temperatures than the prior artsilver-containing alloys, particularly for high silver contents, such as6-18% and will exhibit greater corrosion resistance. The liquidus andMTA temperatures of brazing alloys of the present invention more closelyrepresent the most important characteristic of where the alloy flows(the working temperature). The filler metal can readily fill looseconnections and cap large copper fittings. Specific formulations of thisalloy can accommodate near-eutectic melting characteristics to brazetight-fitting parts and conversely, to fill loose connections as largeas 0.050″.

The large caps formed by brazing with the phos-copper base alloycompositions of the present invention (without silver addition) are abright tin or silver color, and their presence is easily seen. This isan advantage over the phos-copper alloys of the prior art that do notcap well and are black in color after brazing. The brazing torchoperator has great difficulty viewing the previous copper brazes becausethe braze itself is black from oxide as is the copper adjacent to thebraze. This can contribute to leaks in the manufacturing of suchcomponents as air conditioning copper coils, leaks that can be avoidedby the operator's being able to see a bright metal braze (cap or seal)that is contiguous and complete. The phosphorus-tin-nickel-copper alloysand the phosphorus-tin-nickel-silicon-copper alloys of the presentinvention cause no blackening on the braze or on the adjacent copper.

To this end, a solid brazing component is provided as a strip, foil,wire or preform, wherein the brazing component has a liquidustemperature above 840° F., thus making the component suitable forbrazing techniques. The brazing component is made of an alloy consistingessentially of, in weight percent, about 4-9% phosphorus, about 0.1-10%tin, and about 0.1-15% nickel. In all alloy examples provided herein,the balance of the composition is copper. Further, in all alloysdescribed herein, all or a portion of the tin may be replaced byantimony, which serves the same or similar function in the alloy, butpreferably the antimony content does not exceed about 4%, and the sum oftin and antimony does not exceed about 10% of the alloy composition. Thepresence of nickel in combination with tin results in a lowering of thesolidus temperature, an increase in hardness, and an improvement incorrosion resistance. Advantageously, nickel is included in an amount ofabout 3-10%. It may be appreciated that as nickel content increases,fabrication becomes increasingly more difficult in proportion, namelyextrusion and drawing into wire becomes more difficult. Thus, tooptimize corrosion resistance and extrudability, the alloyadvantageously includes about 5-8% Ni.

The alloys of the present invention may further include up to about 3%silicon, and advantageously include silicon in an amount of about0.001-3%. In another exemplary embodiment of the present invention, thealloys may further include up to 18% silver, and advantageously containsilver in an amount of about 1-18%. In yet-another exemplary embodimentof the present invention, the alloy includes both silver and siliconadditions. All alloys of the present invention may further include up toabout 3% manganese without departing from the scope of the presentinvention. Manganese is a known alloying addition for increasing thetoughness and hardness of the brazing alloy. Further, alloys includingimpurity amounts of other elements are considered within the scope ofthe present invention. Impurities may be present by virtue of the rawmaterials used to make the alloys, and are to be distinguished fromelements intentionally added to the alloy melt for the purpose ofaffecting the properties of the alloy.

As may be appreciated by one skilled in the art, variations in theamounts of each of the alloying elements, within the above-describedranges, will have an effect on the liquidus, MTA and solidustemperatures of the brazing alloy, as well as hardness and corrosionresistance. The following alloys are provided as exemplary, in that theyachieve desirable liquidus, MTA, and/or solidus temperatures, achievegood corrosion resistance, form a substantial cap or shoulder, andproduce little to no blackening on the braze or adjacent metal. In noway should the following recitations be considered to limit the scope ofthe present invention to the specific exemplary alloys. A firstexemplary embodiment of a brazing component of the present invention ismade of an alloy consisting essentially of, in weight percent: (a) about4-9% phosphorus; (b) about 4-8% tin; (c) about 5-8% nickel, and thebalance copper. Optional additional elements may include up to 3%silicon, up to 4% antimony, up to 18% silver and up to 3% manganese.

A second exemplary embodiment of a brazing component of the presentinvention is made of an alloy consisting essentially of, in weightpercent: (a) about 4-9% phosphorus; (b) about 4-8% tin; (c) about 3-10%nickel, (d) about 2-18% silver, and the balance copper. Optionaladditional elements may include up to 3% silicon, up to 4% antimony andup to 3% manganese.

A third exemplary embodiment of a brazing component of the presentinvention is made of an alloy consisting essentially of, in weightpercent: (a) about 4-7% phosphorus; (b) about 4-8% tin; (c) about 5-8%nickel; (d) about 6-15% silver; (e) about 0.001-1% silicon, and thebalance copper. Optional additional elements may include up to 4%antimony and up to 3% manganese.

A fourth exemplary embodiment of a brazing component of the presentinvention is made of an alloy consisting essentially of, in weightpercent: (a) about 5-6% phosphorus; (b) about 6-7% tin; (c) about 5-8%nickel; (d) about 6-10% silver, (c) about 0.015-0.02% silicon, and thebalance copper. Optional additional elements may include up to 4%antimony and up to 3% manganese.

A fifth exemplary embodiment of a brazing component of the presentinvention is made of an alloy consisting essentially of, in weightpercent: (a) about 5-6% phosphorus; (b) about 6-7% tin; (c) about 5-8%nickel; (d) about 15% silver; (e) about 0.015-0.02% silicon, and thebalance copper. These alloys may exhibit a solidus temperature on theorder of 1034-1056° F. and a liquidus temperature on the order of about1404° F. or less, as well as a MTA on the order of 1205-1296° F.Optional additional elements may include up to 4% antimony and up to 3%manganese.

The above-described alloy components are added to a melt in desiredamounts, and the resulting alloy melt is continuously cast into abillet. The billet is then extruded into a wire or rolled into strip orfoil. The wire may be drawn one or more times to produce a desired wirediameter. If desired, the wire may be further formed into a preform.

A joint is brazed in accordance with the present invention by placingthe solid brazing component having one of the compositions describedabove between two metal parts, heating the solid brazing component tomelt at least a major portion of the alloy (i.e., heating to a brazingtemperature at or near the MTA or liquidus temperature) to cause thealloy to wet and flow between the two metal parts, with flux ifnecessary, then cooling the alloy to form the brazed joint, whereby araised cap is visible between the two metal parts, and the joint andadjacent metal parts are substantially free of black metal oxide. In oneembodiment, the metal parts may be two copper or copper alloy parts andthe brazed joint will be visually distinguishable from the parts, havinga bright tin or silver color. The solid brazing components of thepresent invention are suitable for brazing a wide variety of parts ofboth simple and intricate shapes. For example, the brazing componentsare suitable for brazing tubular shaped parts, whereas powder brazingalloys of the prior art are not easily used in that environment. In anexemplary embodiment of the method of the present invention, the solidbrazing component is heated to a temperature less than 1410° F., byvirtue of the alloy having a liquidus and/or MTA temperature below 1410°F. In a further exemplary embodiment of the present invention, the solidbrazing component is heated to a temperature less than 1300° F., byvirtue of the alloy having a liquidus and/or MTA temperature below 1300°F.

The alloys of the present invention, in their broadest form, consistessentially of at least copper, phosphorus, tin (and/or antimony) andnickel. Nickel, in combination with tin, achieves benefits to a degreenot obtainable by the addition of either element alone to thephos-copper base alloys. Nickel, in combination with tin and optionallysilicon, in the phos-copper and silver-phos-copper base alloys, isresponsible for lowering the melting range of the brazing alloy,increasing corrosion-resistance, and smoothing the surface of thefinished braze area. The hardness of the phos-copper base alloys mayalso be increased by nickel addition, particularly with respect to aconstant phosphorus content. However, if nickel content is increasedwhile decreasing phosphorus content, a decrease in hardness may result.By way of example, an alloy of the present invention consistingessentially of 7.1% phosphorus, 6% tin, and 1-8% nickel, balance copper,tests to a Rockwell B hardness of 85-91, whereas the BCuP-2 alloy of theprior art (alloy 1 in the Table below) tests to a lower Rockwell Bhardness of 78. The resultant brazes from alloys of the presentinvention are also ductile and strong. As with BCuP alloys of the priorart, it is important for the base metal to fail rather than the brazedjoint. Several destructive tests on copper brazes made withCu—P—Sn—Ni—Si alloys of the present invention conducted by the EdisonWelding Institute did result in failure of the base metal, rather thanthe brazed joint. Moreover, compared to Cu—P and Cu—P—Ag alloys of theprior art, Cu—P—Sn—Ni and Cu—P—Ag—Sn—Ni alloys of the present inventionexhibit lower liquidus, MTA and/or solidus temperatures and greatercorrosion resistance thereby allowing brazing to take place within alower temperature range and use to occur in more corrosive environmentswith longer joint life. Silicon addition to these alloys also createsthe advantage of lowering the brazing temperature and surface tensionwhen they are in the molten state. This allows the brazing alloys tobetter penetrate tightly fitting parts and to achieve fuller coverage ofthe surfaces to be brazed. For example, leaks in copper coils used inair conditioning systems are often caused by small voids within a braze,connecting with one another, to form a path wherein refrigerant gasesescape.

Silicon additions in the presence of tin also offer the advantage ofchanging the color and texture of phos-copper base brazes from a dull,grainy, brown finish to a very smooth finish of bright tin or silvercolor. To achieve this color and texture change, these alloys require atin or antimony content of not less than 0.1% and not greater than 10%individually or in combination. In particular, when added in thepresence of tin (0.1% to 8.0%) and/or antimony (up to 4.0%), a colorchange is effected to a bright tin or silver color finish after brazing.Nickel addition increases the degree of this color change, inparticular, the brightness. Silicon addition also increases the averagetensile strength of phos-copper alloys.

Cooling curves run on a phos-copper BCuP-2 braze alloy (alloy 1), BCuP-4braze alloy (alloy 2), and BCuP-5 braze alloy (alloy 3) of the prior artand phos-copper base alloys of the present invention containing tin andnickel additions with or without silicon and/or silver additions areanalyzed and the results set forth the Table, showing solidus, MTA andliquidus temperatures. Minor thermal arrests often appear in the coolingcurves but are not shown. All values are percents by weight.

% % % % % Liquidus MTA Solidus Alloy P Ag Sn Ni Si ° F. ° F. ° F.  1*7.1 — — — — 1475 — 1310  2** 7.2  6 — — — 1335 1246 1190  3*** 5 15 — —— 1480 1194 1190  4 5 15 6 5 0.02 1343 1293 1037  5 5 15 6 5 — 1352 12111037  6 5 15 6 6 0.02 1352 1205 1038  7 5 15 6 7 0.02 1353 1251 1034  85 15 6 8 0.02 1384 1296 1034  9 5 15 6 6  0.015 1404 1212 1056 10 7  6 66  0.015 1240 1114 1037 11 5 6 6  0.015 1134 — 1134 12 7.1 — 6 1 — 1241— 1241 13 7.1 — 6 3 — 1264 1210 1098 14 7.1 — 6 5 — 1290 1178 1116 157.1 — 6 8 — 1359 1133 1098 *Prior art phos-copper brazing alloy known asBCuP-2 **Prior art silver-phos-copper brazing alloy known as BCuP-4***Prior art silver-phos-copper brazing alloy known as BCuP-5

The Table illustrates significant reductions in temperature across themelting range of the phos-copper base alloys of the present invention ascompared with the BCuP-2 brazing alloy (alloy 1) of the prior art.Brazing temperatures for the phos-copper alloys with tin and nickeladditions are significantly lower than the phos-copper BCuP-2 brazingalloys. The higher the nickel content, the lower the brazingtemperature. The substantial reduction of required brazing temperatureseffects considerable savings of both fuel gases and cycle time ofbrazing operations. The lower brazing temperatures also lessen thedegree of annealing caused to parent copper and brass metals with thephos-copper base alloys. Such annealing causes the metal to soften andto become very weak. Also, in some very hot brazing furnaces, slightmelting of the copper or brass base parts can occur.

A comparison of alloys 12-15 of the present invention show the effect ofadding 6% tin in combination with 1-8% nickel to the BCuP-2 alloy. Thecombination of 6% tin and 1% nickel drops both the liquidus and solidustemperatures to 1241° F. As nickel content increases, the solidustemperature drops further, and the liquidus increases, but a MTA occurs,and brazing occurs at or near the MTA.

A comparison of alloy 11 of the present invention with the BCuP-2 alloy(alloy 1) of the prior art demonstrates the synergistic effect achievedby the addition of silicon, tin and nickel in accordance with thepresent invention. The BCuP-2 alloy does not exhibit a MTA, and sobrazing occurs at or near the liquidus temperature of 1475° F. Additionof 6% tin in combination with 6% nickel and 0.015% silicon achieves alowering of both the solidus and liquidus temperatures to 1134° F.

A reduction in brazing temperature is also generally apparent in thesilver-phos-copper alloys containing tin and nickel, in particular thosefurther containing silicon, and more in particular for those alloyscontaining about 6-15% silver. Alloy 10 of the present invention incomparison to the BCuP-4 alloy (alloy 2) demonstrates that the additionof tin, nickel and silicon lowers the MTA, solidus and liquidustemperatures of the brazing alloy. Alloys 4-9 of the present inventionin comparison to the BCuP-5 alloy (alloy 3) further demonstrate adecrease in the liquidus and solidus temperatures while maintaining orslightly increasing the MTA temperature. In each of the alloys of thepresent invention, the liquidus temperature is below 1410° F. and thesolidus temperature is below 1250° F. Many of the alloys also exhibit anMTA temperature less than 1300° F. Exemplary alloys of the presentinvention have a brazing temperature (MTA or liquidus temperature) below1300° F., and advantageously, below 1250° F.

FIGS. 1 and 2 visually demonstrate the synergistic effect of tin andnickel in the silver-phos-copper alloys and the phos-copper alloys. FIG.1 depicts the corrosion resistance for silver phos-copper alloys of thepresent invention compared to the BCuP-5 alloy (alloy 3), and also tothe BCuP-4 (alloy 2) and BCuP-2 (alloy 1) alloys. The graph includesdata for alloy 4 and alloys similar to alloys 6-8 of the Table. It isnoted that the silicon content varies from that listed for alloys 6-8 inthe Table. Nonetheless, the alloys in FIG. 1 will be referred to asalloys 6-8. Alloys 4 and 6-8 are similar to BCuP-5, but modified with 6%tin; 5, 6, 7 and 8% nickel; and 0.02% silicon addition (or 0 or 0.015),i.e., Cu-5P-15Ag-6Sn-5-8Ni-0.02Si. To simulate a brazed joint in acorrosive environment, a sample of each of the braze alloys was agitatedin a 10% HCl solution for 64 hours, and the weight loss measured. Theresults were extrapolated to predict the extent of corrosion after aperiod of one year. If a sample was made of a silver-phos-copper brazingmaterial, the thickness of the sample would be reduced through corrosionby the amount shown in on year's time. It is noted, however, that eachsurface of the sample was exposed to acid in this test and therebysubject to corrosion, whereas only one surface of a braze is likelyexposed in actual use. Therefore, the extent of corrosion is exaggeratedin this test. Nonetheless, for purposes of comparison, if alloy 4 (5%Ni) were completely exposed to a 10% hydrochloric acid (HCl) solutionfor one year, the thickness of the braze would decrease by 0.127 inch. Abraze of an alloy similar to alloy 8 (8% Ni) would decrease in thicknessby 0.105 inch. So, the 8% Ni alloy 8 is about 17% more corrosionresistant than the 5% Ni alloy 4 when exposed to HCl. The BCuP-5 alloywould decrease in thickness by 0.147 inch, and thus, the 5% Ni alloy 4is about 14% more corrosion resistant than BCuP-5 when exposed to HCL,and 8% Ni alloy 8 is about 29% more corrosion resistant than BCuP-5.FIG. 1 also compares the silver phos-copper alloys having 5-8% Ni to theBCuP-2 and BCuP-4 alloys of the prior art. In addition to the 14%improvement over BCuP-5, a braze of a BCuP-4 alloy would decrease inthickness by 0.17 inch, such that the 5% Ni alloy 4 is about 25% morecorrosion resistant. A braze of a BCuP-2 alloy would decrease inthickness by 0.173 inch. So, the 5% Ni alloy 4 is about 27% morecorrosion resistant than BCuP-2 when exposed to HCl.

FIG. 2 depicts the corrosion resistance for phos-copper alloys 13-15 ofthe present invention, as set forth in the Table, compared to the BCuP-2alloy (alloy 1), as well as the BCuP-4 (alloy 2) and BCuP-5 (alloy 3)alloys, of the prior art. The 3% Ni alloy 13 would decrease in thicknessby about 0.065 inch, and thus, is about 62% and 56% more corrosionresistant than 13CuP-2 and BCuP-5, respectively, when exposed to HCL.The 8% Ni alloy 15 would decrease in thickness by about 0.023 inch, andthus, is about 87% and 84% more corrosion resistant than BCuP-2 andBCuP-5, respectively.

FIGS. 1 and 2 thus demonstrate that high nickel additions may be addedto the silver-phos-copper base alloys and phos-copper base alloys whenaccompanied by tin to provide an alloy suitable for brazing that forms asmooth, solid, visually distinguishable brazed joint with significantlyincreased corrosion resistance.

The Table and Figures show meaningful reductions in liquidus, MTA andsolidus temperatures and increases in corrosion resistance for theCu—P—Sn—Ni and Cu—P—Sn—Ni—Si alloys of the present invention compared tothe BCuP-2 alloy (alloy 1), and for the Cu—P—Ag—Sn—Ni—Si andCu—P—Ag—Sn—Ni alloys of the present invention compared to the BCuP-4(alloy 2) and BCuP-5 (alloy 3) alloys. Further, the brazed joints usingalloys of the present invention have substantial raised shoulders orcaps about the brazed joint which are visually distinguishable fromadjacent copper and copper alloys. There is a further absence of blackoxide, which can obscure the operator's view of the soundness of thejoint. A synergistic effect is achieved with the combined additions oftin and nickel and with tin, nickel and silicon in both phos-copper andsilver-phos-copper alloys.

While the present invention has been illustrated by the description ofan embodiment thereof, and while the embodiment has been described inconsiderable detail, it is not intended to restrict or in any way limitthe scope of the appended claims to such detail. Additional advantagesand modifications will readily appear to those skilled in the art. Theinvention in its broader aspects is therefore not limited to thespecific details, representative apparatus and method and illustrativeexamples shown and described. Accordingly, departures may be made fromsuch details without departing from the scope or spirit of the generalinventive concept.

1. A method of forming a solid brazing component having a liquidustemperature above 840° F. comprising the steps of: forming an alloy meltconsisting essentially of, in weight percent: (a) about 4-9% phosphorus;(b) about 0.1-10% tin; (c) about 0.1-15% nickel; (d) up to about 18%silver; (e) up to about 3% silicon; (f) up to about 4% antimony; (g) upto about 3% manganese; and the balance copper; continuously casting thealloy melt into a billet; fabricating the billet into a solid brazingcomponent selected from the group consisting of wire, strip, foil andpreform.
 2. The method of claim 1 wherein the billet is fabricated intoa wire by extrusion, the method further comprising drawing the wire oneor more times to a final desired thickness.
 3. The method of claim 2further comprising forming the wire into a preform.
 4. A method offorming a brazed joint comprising the steps of: forming a solid brazingcomponent by the method of claim 1; placing the solid brazing componentbetween two metal parts; heating the solid brazing component to melt atleast a major portion of the alloy to cause the alloy to wet and flowbetween the two metal parts; cooling the alloy to form a brazed jointwith a raised cap between the two metal parts, wherein the brazed jointis substantially free of black metal oxide.
 5. The method of claim 4wherein the solid brazing component is placed between two copper alloyparts and the brazed joint is visually distinguishable from the parts.6. The method of claim 4 wherein the solid brazing component is placedbetween two tubular shaped parts.
 7. The method of claim 4 wherein thesolid brazing component is heated to a temperature less than 1410° F. tomelt the major portion.
 8. The method of claim 4 wherein the solidbrazing component is heated to a temperature less than 1300° F. to meltthe major portion.